Larvicidal Enzyme Inhibition and Repellent Activity of Red Mangrove Rhizophora mucronata (Lam.) Leaf Extracts and Their Biomolecules Against Three Medically Challenging Arthropod Vectors.

The larvicidal potential of crude leaf extracts of Rhizophora mucronata, the red mangrove, using diverse solvent extracts of the plant against the early fourth instar larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti mosquito vectors was analyzed. The acetone extract of R. mucronata showed the greatest efficacy: for Cx. quinquefasciatus (LC50 = 0.13 mg/mL; LC90 = 2.84 mg/mL), An. stephensi (LC50 = 0.34 mg/mL; LC90 = 6.03 mg/mL), and Ae. aegypti (LC50 = 0.11 mg/mL; LC90 = 1.35 mg/mL). The acetone extract was further fractionated into four fractions and tested for its larvicidal activity. Fraction 3 showed stronger larvicidal activity against all the three mosquito larvae. Chemical characterization of the acetone extract displayed the existence of several identifiable compounds like phytol, 3,7,11,15-tetramethyl-2-hexadecen-1-ol, 1-hexyl-2-nitrocyclohexane, eicosanoic acid etc. Enzyme assay displayed that R. mucronata active F3-fractions exert divergent effects on all three mosquitos' biochemical defensive mechanisms. The plant fractions displayed significant repellent activity against all the three mosquito vectors up to the maximum repellent time of 210 min. Thus, the bioactive molecules in the acetone extract of R. murconata leaves showed significant larvicidal and enzyme inhibitory activity and displayed novel eco-friendly tool for mosquito control.

Multipurpose efficacy of the lyophilized cell-free supernatant of Salmonella bongori isolated from the freshwater fish, Devario aequipinnatus: toxicity against microbial pathogens and mosquito vectors.

Presently, the discovery of effective drugs and pesticides from eco-friendly biological sources is an important challenge in the field of life sciences. The present research was aimed for standardizing an innovative approach in the evaluation of the biological potentiality of the metabolites of fish-associated bacteria. We have identified 17 skin-associated bacteria from the freshwater fish, giant danio, Devario aquipinnatus. They were screened through biofilm forming and extracellular enzyme producing ability. The results of preliminary antibacterial evaluation of the bacterial supernatants underlined the importance of three potential strains (BH8, BH10 and BH11) for further applied research. Hence, such strains were subsequently subjected to a novel extraction procedure to overcome the difficulties found in polar solvents mixed with the supernatant. The lyophilized cell-free supernatant (LCFS) of 3 isolates were individually extracted by using methanol. During the testing of LCFS's methanolic extract (LCFS-ME) of 3 isolates, only the extract of BH11-strain exhibited potent inhibitory activity against the pathogenic bacteria and fungi. Furthermore, the larvicidal and mosquitocidal assays on the filariasis vector, Culex quinquefasciatus also showed its potent toxicity on both the adults and developmental instars of mosquito. Through molecular and phylogenetic analyses, the BH11 strain was identified as Salmonella bongori (KR350635). The present finding emphasized that the S. bongori could be an important novel source of effective antimicrobials and mosquitocidal agents.

Larvicidal activity of green synthesized silver nanoparticles using bark aqueous extract of Ficus racemosa against Culex quinquefasciatus and Culex gelidus

OBJECTIVE@#To investigate the larvicidal activity of synthesized silver nanoparticles (Ag NPs) utilizing aqueous bark extract of Ficus racemosa (F. racemosa) was tested against fourth instar larvae of filariasis vector, Culex quinquefasciatus (Cx. quinquefasciatus) and japanese encephalitis vectors, Culex gelidus (Cx. gelidus).@*METHODS@#The synthesized Ag NPs was characterized by UV-vis spectrum, X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). The larvicidal activities were assessed for 24 h against the larvae of Cx. quinquefasciatus and Cx. gelidus with varying concentrations of aqueous bark extract of F. racemosa and synthesized Ag NPs. LC(50) and r(2) values were calculated.@*RESULTS@#The maximum efficacy was observed in crude aqueous extract of F. racemosa against the larvae of Cx. quinquefasciatus and Cx. gelidus (LC(50)=67.72 and 63.70 mg/L; r(2)=0.995 and 0.985) and the synthesized Ag NPs (LC(50)=12.00 and 11.21 mg/L; r(2)=0.997 and 0.990), respectively. Synthesized Ag NPs showed the XRD peaks at 2 θ values of 27.61, 29.60, 35.48, 43.48 and 79.68 were identified as (210), (121), (220), (200) and (311) reflections, respectively. The FTIR spectra of Ag NPs exhibited prominent peaks at 3,425, 2,878, 1,627 and 1,382 in the region 500-3,000 cm(-1). The peaks correspond to the presence of a stretching vibration of (NH) C=O group. SEM analysis showed shape in cylindrical, uniform and rod with the average size of 250.60 nm.@*CONCLUSIONS@#The biosynthesis of silver nanoparticles using bark aqueous extract of F. racemosa and its larvicidal activity against the larvae of disease spreading vectors. The maximum larvicidal efficacy was observed in the synthesized Ag NPs.

Acaricidal activity of synthesized titanium dioxide nanoparticles using Calotropis gigantea against Rhipicephalus microplus and Haemaphysalis bispinosa

OBJECTIVE@#To assess the acaricidal activity of titanium dioxide nanoparticles (TiO2 NPs) synthesized from flower aqueous extract of Calotropis gigantea(C. gigantea) against the larvae of Rhipicephalus (Boophilus) microplus [R. (B.) microplus] and the adult of Haemaphysalis bispinosa (H. bispinosa).@*METHODS@#The lyophilized C. gigantea flower aqueous extract of 50 mg was added with 100 mL of TiO(OH)2 (10 mM) and magnetically stirred for 6 h. Synthesized TiO2 NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy dispersive X-ray spectroscopy (EDX). The synthesised TiO2 NPs were tested against the larvae of R. (B.) microplus and adult of H. bispinosa were exposed to filter paper impregnated method.@*RESULTS@#XRD confirmed the crystalline nature of the nanoparticles with the mean size of 10.52 nm. The functional groups for synthesized TiO2 NPs were 1 405.19, and 1 053.45 cm(-1) for -NH2 bending, primary amines and amides and 1 053.84 and 1 078.45 cm(-1) for C-O. SEM micrographs of the synthesized TiO2 NPs showed the aggregated and spherical in shape. The maximum efficacy was observed in the aqueous flower extract of C. gigantea and synthesized TiO2 NPs against R. (B.) microplus (LC50=24.63 and 5.43 mg/L and r(2)=0.960 and 0.988) and against H. bispinosa (LC50= 35.22 and 9.15 mg/L and r(2) = 0.969 and 0.969), respectively.@*CONCLUSIONS@#The synthesized TiO2 NPs were highly stable and had significant acaricidal activity against the larvae of R. (B.) microplus and adult of H. bispinosa. This study provides the first report of synthesized TiO2 NPs and possessed excellent anti-parasitic activity.

Efficacy of larvicidal and pupicidal activity of Catharanthus roseus aqueous and solvent extracts against Anopheles stephensi Liston and Culex quinquefasciatus Say (Diptera: Culicidae)

OBJECTIVE@#To investigate the larvicidal and pupicidal activities of aqueous, ethyl acetate and methanol extracts of Catharanthus roseus (C. roseus) against malaria and filariasis vectors.@*METHODS@#The larvicidal and pupicidal activities of C. roseus leaf extracts were tested against the fourth instar larvae and pupae of Anopheles stephensi (An. stephensi) and Culex quinquefasciatus (Cx. quinquefasciatus). The mortality was observed after 24 and 48 h post the treatment. The data were subjected to probit analysis to determine the lethal concentrations (LC50 and LC90) at which 50% and 90% of the treated larvae or pupae of the tested species were killed.@*RESULTS@#The larval and pupal mortality were observed after 24 and 48 h of exposure of aqueous, ethyl acetate and methanol extracts of C. roseus; no mortality was observed in the control group. The LC50 values against the fourth-instar larvae of An. stephensi were 68.62 and 72.04 mg/mL for the aqueous extract, 82.47 mg/mL for the ethyl acetate extract, and 78.80 and 86.64 mg/mL for the methanol extract, while the aqueous, ethyl acetate and methanol extracts had LC50 values of 85.21, 76.84 and 94.20 mg/mL against the fourth-instar larvae of Cx. quinquefasciatus. The aqueous, ethyl acetate and methanol extracts had LC50 values of 118.08, 182.47 and 143.80 mg/mL against the pupae of An. stephensi and 146.20, 226.84 and 156.62 mg/mL against the pupae of Cx. quinquefasciatus, respectively.@*CONCLUSIONS@#The aqueous and methanol extracts of C. roseus leaves had an excellent potential to control the malarial vector An. stephensi and filariasis vector Cx. quinquefasciatus.

Larvicidal and repellent activity of medicinal plant extracts from Eastern Ghats of South India against malaria and filariasis vectors

OBJECTIVE@#To evaluate the larvicidal and repellent activities of ethyl acetate and methanol extracts of Acacia concinna (A. concinna), Cassia siamea (C. siamea), Coriandrum sativum (C. sativum),Cuminum cyminum (C. cyminum), Lantana camara (L. camara), Nelumbo nucifera (N. nucifera) Phyllanthus amarus (P. amarus), Piper nigrum (P. nigrum) and Trachyspermum ammi (T. ammi) against Anopheles stephensi (An. stephensi) and Culex quinquefasciatus (Cx. quinquefasciatus).@*METHODS@#The larvicidal activity of medicinal plant extracts were tested against early fourth-instar larvae of malaria and filariasis vectors. The mortality was observed 24 h and 48 h after treatment, data were subjected to probit analysis to determine the lethal concentrations (LC(50) and LC(90)) to kill 50 and 90 per cent of the treated larvae of the tested species. The repellent efficacy was determined against two mosquito species at five concentrations (31.25, 62.50, 125.00, 250.00, and 500.00 ppm) under the laboratory conditions.@*RESULTS@#All plant extracts showed moderate effects after 24 h and 48 h of exposure; however, the highest activity was observed after 24 h in the leaf methanol extract of N. nucifera, seed ethyl acetate and methanol extract of P. nigrum against the larvae of An. stephensi (LC(50) = 34.76, 24.54 and 30.20 ppm) and against Cx. quinquefasciatus (LC(50) = 37.49, 43.94 and 57.39 ppm), respectively. The toxic effect of leaf methanol extract of C. siamea, seed methanol extract of C. cyminum, leaf ethyl acetate extract of N. nucifera, leaf ethyl acetate and methanol extract of P. amarus and seed methanol extract of T. ammi were showed 100% mortality against An. stephensi and Cx. quinquefasciatus after 48 h exposer. The maximum repellent activity was observed at 500 ppm in methanol extracts of N. nucifera, ethyl acetate and methanol extract of P. nigrum and methanol extract of T. ammi and the mean complete protection time ranged from 30 to 150 min with the different extracts tested.@*CONCLUSIONS@#These results suggest that the leaf and seed extracts of C. siamea, N. nucifera, P. amarus, P. nigrum and T. ammi have the potential to be used as an ideal ecofriendly approach for the control of the An. stephensi and Cx. quinquefasciatus.